How should the concentrator's shield ground be connected to the power ground?

The connection between the shielding ground (cable shielding layer, shielding cover) and the protective earth (PE) in the concentrator directly affects the shielding effectiveness and safety. The basic principle is that the shielding ground should be connected to the chassis (i.e., PE) at the equipment entrance with low impedance and a large area, and only at this one point. Specific implementation: When all external shielded cables enter the concentrator, the shielding layer should be pressed 360° against the metal surface of the chassis using metal cable joints (gland) or shielding clamps. The chassis itself should be reliably connected to the PE line.

The shielding cover on the PCB should be connected to the chassis via multiple spring fingers or conductive foam. It is forbidden to introduce the cable shielding layer into the PCB, connect it to the signal ground, and then transfer it to PE. For independent shielding boxes for internal sensitive modules, a high-frequency capacitor (e.g., 10nF) can be connected to the PCB analog ground, while the box is insulated from the chassis. In this way, external interference is directly discharged to PE through the shielding layer and does not enter the circuit. Correct connection ensures that the shielding layer's suppression effect on high-frequency interference exceeds 30dB.